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Re: [Xen-devel] [PATCH 0/4] ARM: ACPI: ITS: Add ITS Support for ACPI hardware domain

On 10/08/17 13:00, Manish Jaggi wrote:
Hi Julien,

On 8/10/2017 4:58 PM, Julien Grall wrote:

On 10/08/17 12:21, Manish Jaggi wrote:
Hi Julien,

On 6/21/2017 6:53 PM, Julien Grall wrote:
Hi Manish,

On 21/06/17 02:01, Manish Jaggi wrote:
This patch series adds the support of ITS for ACPI hardware domain.
It is tested on staging branch with has ITS v12 patchset by Andre.

I have tried to incorporate the review comments on the RFC v1/v2
The single patch in RFC is now split into 4 patches.

I will comment here rather than on each patches.

Patch1: ARM: ITS: Add translation_id to host_its
 Adds translation_id in host_its data structure, which is populated
 translation_id read from firmwar MADT. This value is then programmed
 local MADT created for hardware domain in patch 4.

I don't see any reason to store value that will only be used for
generating the MADT which BTW is just a copy for the ITS. Instead we
should copy over the MADT entries.

There are two approaches,

If I use the standard API  acpi_table_parse_madt which would iterate
over ACPI_MADT_TYPE_GENERIC_TRANSLATOR entries, I have to maintain the
addr and translation_id in some data structure, to be filled later in
the hwdomain copy of madt generic translator.

If I don't use the standard API I have to add code to manually parse all
the translator entries.

There are a 3rd approach I suggested and ignored... The ITS entries
for Dom0 is exactly the same as the host entries.
Yes, and if not passed properly dom0 wont get device interrupts...
So you only need to do a verbatim copy of the entry...

Can you please check patch 4/2, the translation_id and address are
passed verbatim, the other values are reserved in

For ACPI, we took the approach to only rewrite what's necessary and give the rest to Dom0 as it is. If newer version of ACPI re-used those fields, then they will be copied over to Dom0. I don't consider it as an issue because the problem would be the same if those fields have an important meaning for the platform.

Could you please detail 3rd approach and how different it is from
approach 2.

ACPI_MEMCPY(its, host_its, size);


Julien Grall

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